Xanthomonas citri subsp. citri (Xcc) is the etiological agent of citrus canker, a disease that affects almost all types of citrus crops. Production of Xcc virulence factors is controlled by a gene cluster rpf, which encodes elements of a cell-cell communication system called quorum sensing (QS). Perturbation of cell-cell signaling systems either by signal degradation or by overproduction significantly reduces symptoms and thereby the severity of the disease. Pathogenicity assays in Citrus sinensis showed that some bacterial species natural inhabitants of citrus phyllosphera have the strong ability to disturb QS system mediated by diffusible signal factor (DSF) molecule in Xcc and to reduce disease severity. The lessening of symptoms was associated with alteration in bacterial attachment and biofilm formation. These factors are known to contribute to Xcc virulence in the early stages of disease. The aim of this chapter is to review QS system in Xcc, the virulence factors affected by QS disturbing, as well as the main secretion systems that participate actively in virulence and its effect on the symptomatology of citrus canker.
Part of the book: Citrus Pathology